1. Field of the Invention
This invention pertains to the removal of particulate matter from particulate laden gases. In particular, this invention directs itself to the cleansing of waste gases which are the products of combustion containing particulates and gaseous pollutants. Still further, this invention directs itself to a system and method for removing particulates from waste gases which is capable of removing particulates in the micron and less range which may result from a number of processes such as coal combustion. Additionally, the subject invention is directed to a system and method wherein phoretic forces are used in combination with gravity to capture particulates from a waste gas. Still further, the subject invention is directed to a system and method wherein the particulate matter in the waste gas is driven through a zone of sustained supersaturation, and thus accelerating the nucleation and growth of particulate matter. Rapid growth of submicron particles enhances the action of gravitational force which in combination with phoretic forces drives the particulate matter to a capturing mechanism for removal from the system.
2. Prior Art
Removal of particulate matter from waste gases has been a continuing concern in industry for a number of years. Particle removing systems and methods for removing such particles from waste gases are known in the prior art.
In some prior art systems wet scrubbers are used for removal of particulate matter from waste gases. Generally, such prior art scrubbers are able to attain high collection efficiencies if sufficient energy is applied to the gas and liquid contacting process. However, it has been found that energy costs increase at a very high rate with the decrease in particle size below approximately 3.0 microns. Due to the increased cost of removing fine particulates, work has been directed to particle growth by water condensation in a number of systems such as spray or steam preconditioners and in other wet scrubbing systems.
Some projects have been initiated to investigate the potential of flux force condensation in order to reduce power requirements for fine particulate removal. The particle growth due to water vapor condensation and the collection enhancement by thermophoretic and diffusiophoretic forces are currently being sought in the condenser/wet scrubber from the cooling of hot, humid waste gases by contact with cold water. However, such flux force condensation scrubbing systems do not provide for supersaturation which is necessary for the nucleation of certain water insoluble submicron particles to take place. Such prior systems do not employ sustained supersaturation for the nucleation and growth of fine particulates in the nucleation process.
The closest prior art known to the applicant from a search made at the U.S. Patent and Trademark Office is U.S. Pat. No. 4,497,641. This reference directs itself to a system and method for dust control by condensation enlargement. Thus, particles are enlarged from sizes less than 1 micron to larger sizes by nucleation. This prior art reference system uses a plurality of hot and cold plates where hot water covers the surface of the sides of the hot plates and travels in a downward direction across the surface of the plates. Heaters are used to enhance evaporation and as water evaporates such diffuses across the distance between the hot and cold plates where it contacts the cool surface of the cold plates. The condensation of the water and the dust particles are received at the bottom of an overall housing. However, although such system does use to some extent phoretic forces, such does not provide for the sustained supersaturation concept of the subject invention in combination with the combined phoretic and gravity forces necessary to the subject invention concept.
Other prior art known to the applicant include U.S. Pat. Nos. 3,912,469; 4,141,701, 3,852,409; 3,852,408; 4,272,499; 3,894,851; 3,218,047; 4,375,976; 4,153,432; 4,290,783; 4,193,774; 467,264; 495,359; 3,966,438; 3,696,590; and 2,935,375. None of these references provide for the concept of sustained supersaturation in combination with phoretic and gravity forces for capturing the nucleating particulate matter.